Chemotaxis by a macrophage cell line was inhibited by 3-deazaadenosine but not by 3-deazaaristeromycin. Determination of the change in intracellular levels of S-adenosyl-L-homocysteine (AdoHcy) and 3-deazaadenosylhomocysteine (3-deaza-AdoHcy) showed that inhibition of chemotaxis was correlated with the increase in 3-deaza-AdoHcy, formed intracellularly by the utilization of 3-deazaadenosine as a substrate for AdoHcy hydrolase. Two lipid reactions were tested for susceptibility to inhibition by 3-deazaadenosine and 3-deazaaristeromycin. Both the synthesis of phosphatidylcholine by stepwise methylation of phosphatidylethanolamine and the release of arachidonic acid were inhibited by 3-deazaadenosine and 3-deazaaristeromycin, indicating that these two reactions were not required for chemotaxis. However, the synthesis of a small number of proteins, separated by two-dimensional polyacrylamide gel electrophoresis was susceptible to 3-deazaadenosine, but not to 3-deazaaristeromycin. A correlation was found between inhibition of chemotaxis and inhibition of the synthesis of the same subset of proteins when other compounds were tested. We postulate that incubation of cells with 3-deazaadenosine inhibits a methylation reaction that is required for the formation of a functional mRNA coding for one or more proteins required for chemotaxis.